The UKCA timeline is outlined here
23rd June 2016
The UK votes to leave the European Union
31st January 2020
The UK leaves the European Union
1st February 2020
11 month transition period begins
31st December 2020
End of the transition period
1st January 2021
UKCA mark required for products on UK market
1st January 2022
CE mark no longer accepted in UK
1st January 2023
All UKCA mark to be permanent marking*
*Non-permanent marking is permitted before this date. This can be an adhesive label on the product or packaging. Permanent marking required after this date